Androgen and estrogen, which are sex hormones, have various physiological activities such as differentiation and proliferation of cells and the like. On the other hand, it has been found that androgen and estrogen act as an exacerbation factor in some diseases. It is known that steroid C17,20-lyase is involved in the final stage in the biosynthesis of androgen in vivo. That is, steroid C17,20-lyase converts, as a substrate, 17-hydroxypregnenolone and 17-hydroxyprogesterone derived from cholesterol to dehydroepiandrosterone and androstenedione, respectively. Therefore, a medicine having a steroid C17,20-lyase inhibitory activity suppresses formation of androgen, as well as estrogen produced from androgen as a substrate, and is useful as an agent for the prophylaxis or treatment of diseases whose exacerbation factor is androgen or estrogen. As the disease for which androgen or estrogen is an exacerbation factor, there are mentioned, for example, prostate cancer, prostatic hypertrophy, virilism, hirsutism, male pattern alopecia, precocious puberty, breast cancer, uterine cancer, ovarian cancer, mastopathy, uterus myoma, endometriosis, adenomyosis of uterus, polycystic ovary syndrome, and the like.
Steroid-type compounds and non-steroid-type compounds are already known as steroid C17,20-lyase inhibitors. The steroid-type compounds are disclosed in, for example, WO 92/15404, WO 93/20097, EP-A 288053, EP-A 413270 and the like. As non-steroid-type compounds, for example, (1H-imidazol-1-yl)methyl-substituted benzimidazole derivatives are shown in Japanese Published Unexamined Patent Application No. 85975/1989, carbazole derivatives are shown in WO94/27989, WO96/14090 and WO97/00257, azole derivatives are shown in WO95/09157, 1H-benzimidazole derivatives are shown in U.S. Pat. No. 5,491,161, dihydronaphthalene derivatives are shown in WO99/18075, and naphthalene derivatives are shown in WO99/54309.